Burglar alarm



Jan. 6, 1942. F. H. GULLIKSEN 2,269,340

- BURGLAR ALARM Filed Sept. 7, 19:59

WITNESSES: INVENTOR M v 54 BY 7 Mina Patented Jan. 6, 1942 BURGLAR ALARMFinn H. .Gulliksen, Pittsburgh, Pa., assignor to WestinghouseElectric &Manufacturing Company, East Pittsburgh, Pa., 'a corporationbfPennsylvania Application September 7, 1939, Serial No. 293,730

g 10 claims. My invention relates to electric discharge apparatus andhas particular relation to burglar alarm systems.

An essential desideratum in a burglar alarm system is that it shallresist any attempt of the burglar to render it inoperative.Electrostatic systems provided in accordance with the-teachings of theprior art, of which I am aware, to a certain extent, atisfy thiscondition. In apparatus of this type, the capacity to groundof aconductor of extensive area is varied when the burglar approaches;However, the electrostatic equipment has a rather undesirable feature inthat the capacity varies over a substantial range in response tochanging atmospheric conditions.

To remedy the deficiency of capacity burglar alarm systems,photo-sensitive apparatus has been suggested. However, in this case,difiiculty is encountered because the burglar may, with facility, renderthe system inoperative, by replacing the source which supplies theradiation for energizing the photo-sensitive device by another source,such as a flashlight.

It is accordingly an object of my invention to provide a photo-sensitiveburglar alarm system that shall resist any attempt of a burglar torender it inoperative.

Another object of my invention is to provide a burglar alarm system thatshall not be afiected by varying atmospheric conditions.

A further object of my invention is toprovide a burglar alarm system ofsimple structure that shall resist every attempt of a burglar to renderit inoperative.

A general object of my invention is to so interlock a photo-sensitivesystem'with a source of radiant energy that thesystem shall respond onlyto the. radiant energy from the source.

Another general object of my invention is to provide electric dischargeapparatus so interlocked with a physical disturbance that it shallrespond only to the disturbance.

More specifically stated, it is an object of my invention to provide aphoto-sensitive arrangement which shall have the selective propertiesthatare particularly essential in burglar alarm apparatus.

In accordance with my invention, a screen of radiant energy isprovided'at the entrance of the region to be protected. The radiation isderived from a source, the luminous intensity of which varies with thepotential impressed thereon and impinges on a photo-electric cell. Thecell is connected to the control circuit of an is energized from analternating-current system.

The source of radiant energy is supplied. with alternate half-waves ofthe potential from the alternating-current system.

The interconnection between the photo-cell and. the valve is such that"the current flow through the valve is small as long as the-excitation ofthe cell is constant. To increase the current flow through the valve,the excitation of the cell must be varied at least at a rate which is ofthe'same order of magnitude as the .varia-' tion produced by the source.As long as the radiation from the source continues to excite the cell,the valve is conductive andthe burglar alarm signal is' inactive. When aburglar interrupts the radiation, the valve is rendered non-conductiveand the signal is actuated. If a burglar, understanding the operation ofa photo-electric cell, energizes the photo-electric cell with 'aflashlight while heis' entering the protected region, the signallingequipment operates in spite of the'fiashl'ight. The valve remainsnon-c'onductivewhen the radiation on the cell is uniform as would be thecase for a flashlight.

' It may happen that a particular clever burglar realizes thatinterrupted light is necessary to prevent operation of the signallingequipment.

To preclude the successful" use of interrupted lightythe polarity ofthe'potential impressed on both the radiant energy source and the valveis reversed at intervals of the order of one .minute. The phaserelationship between the potential impressed on the valveand theinterrupted light,

used by the burglar is thus changed periodically, and the signallingequipment operates for one phase position'or the other.

The novel features that I consider characteristic of my invention areset forth with particuasymmetrically conductive discharge valve which 5larity in the'appended claims. The invention itself,"however, both as toits organization, and its method of operation, together with additionalobjects and advantages thereof, will best' be understood from'thefollowing description of a specific embodiment when read in connectionwiththe accompanying drawing, in which the single figure is adiagrammatic view showing an embodiment of my invention.

In the drawing, the invention is shown as used for the purpose ofprotecting a safe I. proach to the safe is covered by a screen ofradiant energy produced by a lamp 3. The lamp 3 is preferably of thetungsten filament type, but the broader aspects of my invention maybepracticed with other luminous sources, such as glow tubes, carbon lampsand the like. The

The al light from the lamp is reflected back and forth, at the approachto the safe by suitable mirrors 5 and disposed above and below the safe.

The light emerging from the approach to the safe I impinges on aphoto-electric cell 9 of the usual emissive type. The cell 9 isconnected in a closed circuit with a resistor H and a directcurrentpotential l3 derived from a suitable alternating-current generator l5,preferably of the usual commercial GO-cycle type, through the secondarysection ll of a suitable transformer l9.

To amplify the output of the cell 9, an electric discharge valve 2| isprovided. Thevalve has an anode 23, a cathode 25, and a controlelectrode 21, and is supplied from the alternating-current source |5through a secondary section 29 of the transformer I9, which is providedwith an intermediate tap 3|. The anode 23 of the valve is connected toone terminal of the secondary section 29 through the exciting coil 33 ofan auxiliary relay 35, and the cathode is connected to the intermediatetap 3|. The control electrode 21 of the valve is connected to the otherterminal through a suitable grid resistor 31. The photo-electric cellcircuit is coupled to the control circuit of the valve 2| through acapacitor 39. The capacitor 39 and the grid resistor 31 are connected inparallel with the resistor H in the cell circuit. The lamp is connectedacross the terminals of the secondary section 29 through a half-waverectifier 4|, which is preferably of the copper copper-oxide type.

The auxiliary relay 33 controls a main relay 43 which, in turn, opensand closes the signalling circuit 45. pendently of the generator |5 froma battery 41 or any other suitable source.

The polarity of the potential impressed on the lamp 3 and the valve 2|is reversed at intervals by a drum switch 49 provided with suitablereversing segments 50 and cooperative brushes 5| and 52. The brushes 5|interconnect the segments and the line conductors 53, and the brushes 52connect the segments'to the primary 54 of the supply transformer Ill.The reversing segments 59 are interrupted in the region in which thereversal takes place, and at this point the switch is provided withauxiliary segments 55 which may be used to maintain any connectionswhich would be opened by the interruption.

When the protecting apparatus'is to be used,

a master switch 51 is closed. The generator I5' is connected to the lineconductors 53 through two of 'the contacts 59 of the switch, while thesignalling circuit 45 is closed through a third contact 6|. If theapparatus is in proper condition for operation, potential is suppliedbetween the electrodes 23, 25 and 21 of the valve l. The potentialimpressed between the control electrode 21 and the cathode 25 by theleft-hand portion of the secondary section 29 is in opposite phase tothe anode-cathode potential impressed by the right-hand portion, and isof sufficient magnitude to maintain the valve 2| non-conductive in theabsence of a counteracting potential.

Counteracting potential is provided by the photo-electric circuit whenthe light from the lamp 3 impinges on the cell 9. Current is supplied tothe lamp only during alternate half periods of the source. During theintervening zero current intervals, the lamp filament coolssubstantially so that light from the lamp fluctuates over a substantialrange and the periodicity of the source and the current flow through thecell The latter circuit is supplied indecircuit fluctuatescorrespondingly. The periodic photo-cell current flow through theresistor and the corresponding potential drop are impressed between thecontrol electrode 21 and the cathode 25 through the capacitor 39. Therelationship between the lamp circuit and the anodecathode circuit ofthe valve is such that the potential impressed from resistor Hcounteracts the blocking potential when the anode-cathode potential ispositive, and, therefore, the valve 2| is conductive while the light isimpinging on the cell.

When the switch 51 is closed, the reversing drum 49 is rotated by amotor 63 connected to the conductor 53. The reversal of the potentialsupplied to the primary 54 of the transformer |9 does not, however,affect the relationship between the valve 2| and the lamp 3, since bothelements are supplied from the transformer.

When the valve 2| is rendered conductive, the auxiliary relay 33 incircuit with the valve is actuated, and its contact 65 closes a circuitthrough the exciting coil 61 of the main relay 43. The latter relay isthen actuated and its contact 59 opens the signalling circuit 45. Theauxiliary segments 55 of the reversing drum 49 short-circuit the contact65 of the auxiliary relay 33 during the reversal, and thus assure thatthe main relay 43 remains energized in spite of the discontinuity in thesupply of power to the transformer l9.

If there should be any defect in the system, as, for example, a burntout lamp or a defective photo-cell or valve, the main relay 43 isdeenergized and the signalling circuit 45 is closed. On the other hand,if there is no defect in the equipment, the relays 33 and 43 areenergized and the signalling equipment is deenergized.

Unauthorized entry into the protected region results in the interruptionof the light impinging on the photo-electric cell 9. Under suchcircumstances, the supply of potential impulses by the resistor II incircuit with the cell 9 is discontinued, and the only potentialimpressed in the control circuit of the valve 2| is that derived fromthe secondary section 29. This potential is of sufficient magnitude torender the valve substantially non-conductive. The relays 33 and 43 arethen deenergized and the signalling equip ment is operated.

If the person desiring entry into the region should excite thephoto-electric cell 9 with a flashlight, the valve 2| would still remainnonconductive. The current flow through the cell is, under suchcircumstances, constant, and the resultant potential dropped across theresistor H is constant. No varying potential is, therefore, impressedacross the grid resistor 31 through the capacitor 39, and the onlypotential in the control circuit is blocking potential derived from thesecondary section 29. If the person should produce interrupted light anduse it for exciting the photo-cell 9, he'would still fail to prevent thesignalling apparatus from operating. The interrupted light would nothave the proper phase relationship for maintaining the valve conductivefor one or the other of the positions of the reversing switch 49. Toprevent a person seeking entry from suppling a lamp circuit similar tothe circuit of lamp 3 from the transformer 9, the transformer should bedisposed within the region covered by the light screen.

Although I have shown and described a certain specific embodiment of myinvention, I am full aware that many modifications thereof are possible.My inventiongtherefore, is not to be restricted exceptinsofar-as isnecessitated by the prior art and by, the spirit of the appended claims.l

I claim as my invention: 1 g

1. In combination, an electric discharge device having a principalcircuit and'a control circuit, said control circuit being of the typewherein a control potential varying in a predetermined sense at at leasta predetermined rate must be impressed to produce substantial currentflow through said principal circuit, mens for impressing a periodicenergizing potential in said principal circuit, means for impressing aperiodic potential in said control circuit, said potential varying inamplitude at at least said predetermined rate and in said sense onlyduring certain portions of the periods of said energizing poten' tial,and means for shifting the phase of both said potentials to the sameextent with respect to a hypothetical reference potential.

2. In combination, an electric discharge device having a principalcircuit and a control circuit, said control circuit being of the typewherein a control potential varying in a predetermined sense at at leasta predetermined rate must be impressed to produce substantial currentflow through said principal circuit, means for impressing a periodicenergizing potential in said principal circuit, means for impressing aperiodic potential varying in amplitude at at least said predeterminedrate and in said sense only during certain portions of the periods ofsaid energizing potential, and means for simultaneously reversing bothsaid potentials.

3. In combination, an electric discharge device having a principalcircuit and a control circuit, said control circuit being of the typewherein a control potential varying at at least a predetermined rate andin a predetermined sense must be impressed to produce substantialcurrent flow through said principal circuit, means for impressing aperiodic energizing potential in said principal circuit and means forimpressing a periodic potential in said control circuit, said potentialvarying in amplitude at at least said predetermined rate and in saidsense only during certain portions of the periods of said energizingpotential.

4. In combination, an electric discharge device having a controlelectrode and a plurality of principal electrodes, means for impressingan alternating potential between said principal electrodes,photo-sensitive means connected to said control electrode in such mannerthat the current flow between said principal electrodes is substantialonly when the excitation of said photosensitive means is varied at apredetermined rate in a predetermined sense, a source for exciting saidphoto-sensitive means, means for energizing said source by impressingthereon alternate halfwaves of said potential and means forsimultaneously reversing said potentials impressed on said principalelectrodes and said source.

5. In combination, an electric discharge device having a controlelectrode and a plurality of principal electrodes, means for impressingan alternating potential between said principal electrodes,photo-sensitive means connected to said control electrode in such mannerthat the current flow between said principal electrodes is substantialonly when the excitation of said photo-sensitive means is varied at apredetermined rate in a predetermined sense, a source comprising anincandescible filament of tungsten or the like for exciting said"'pl'ioto s'ens'itive means, means forenergizi'ng said'sour'ce byinipressing thereon alternate halfewav'esjof said potential andmeans'for simultaneously reversing said potentials impressed on saidprincipal electrodes and said source. g Y

, 6. In combination,..an.asymmetrically conductive electric dischargedevice having a control electrode and a plurality of principalelectrodes, means for impressing an alternating potential between saidprincipal electrodes, photo-sensitive means connected to said controlelectrode in such manner that the current flow between said principalelectrodes is substantial only when the excitation of saidphoto-sensitive means is varied at a predetermined rate in apredetermined sense, a source for exciting said photo-sensitive means,means for energizing said source by impressing thereon alternatehalf-waves of said potential and means for simultaneously reversing saidpotentials impressed on said principal electrodes and said source.

7 For use in signalling an entry into a region, the combinationcomprising, a photo-sensitive device, a source of radiant energy, saidsource and device being so arranged that radiant energy passes from saidsource to said device and forms a screen before said region, an electricdischarge device having a principal circuit and a control circuit, meansfor'impressing an alternating potential in said principal circuit, meansfor energizing said source by impressing alternate halfwaves of saidalternating potential thereon, means for connecting said photo-sensitivedevice in said control circuit in such manner that the current flow insaid principal circuit is substantial only when the radiant energyimpressing on said photo-sensitive device has a rate of variationcorresponding to that of said source and means for simultaneouslyreversing the polarity of the potentials impressed on said principalcircuit and on said source at intervals.

8. For use in signalling an entry into a region, the combinationcomprising, a photo-sensitive device, a source of radiant energy, saidsource and device being so arranged that radiant energy passes from saidsource to said device and forms a screen before said region, an electricdischarge device having a principal circuit and a control circuit, meansfor impressing an alternating potential in said principal circuit, meansfor energizing said source by impressing alternate halfwaves of saidalternating potential thereon, means for connecting said photo-sensitivedevice in said control circuit in such manner that the current flow insaid principal circuit is substantial only when the radiant energyimpressing on said photo-sensitive device has a rate of variationcorresponding to that of said source, means for simultaneously reversingthe polarity of the potentials impressed on said principal circuit andon said source at intervals, signalling means, and means for actuatingsaid signalling when said radiant energy is interrupted or when thesupply of saidalternating potential is discontinued.

9. In combination, an electric discharge device having an anode, acathode, and a control electrode, means for impressing an alternatingpotential between said anode and cathode, a photo-sensitive device,means including a capacitor for connecting said photo-sensitive devicebetween said control electrode and cathode, a source for exciting saidphoto-sensitive device and means for energizing said source withalternate half-waves of said potential.

10. In combination, an electric discharge device having an anode, acathode, and a control electrode, means for impressing an alternatingpotential between said anode and cathode, a photo-sensitive device,means including a capacitor for connecting said photo-sensitive devicebetween said control electrode and cathode, a source for exciting saidphoto-sensitive device, means for energizing said source with alternatehalf-waves of said potential and means for simultaneously reversing thepolarity of the potential impressed between said anode and cathode andon said source.

FINN H. GULLIKSEN.

